1. Field of the Invention
The present invention relates to a shock absorbing apparatus for a steering column which is particularly capable of improving the capability of absorbing an initial shock in a shock absorbing structure which, during the occurrence of a colliding accident of a vehicle, damps a shock, protects a driver, and ensures safety when the driver hits against a steering wheel as a reaction of the collision.
2. Description of the Related Art
A shock absorbing mechanism which, during a collision of a vehicle, absorbs energy occurring when the driver hits against the steering wheel as its reaction, and which damps the shock to protect the driver is conventionally incorporated in the vicinity of a steering column for supporting a steering shaft. Various such shock absorbing mechanisms have been developed, and many of them have been adopted in practice.
As a shock absorbing mechanism of this kind which is widely adopted, there is a type in which a column bracket for mounting the steering column is mounted at a predetermined position in a vehicle body in such a manner as to be movable in the back-and-forth direction. The moving operation of the column bracket is effected by an impact occurring when, during the occurrence of a collision, the driver hits against the steering wheel as a reaction of the collision. A mechanism for imparting resistance to the moving operation is provided at a connecting portion between the column bracket and the mounting portion so as to damp the shock and gradually diminish the force with which the column bracket moves.
The shock damping performance is substantially determined by the relative magnitude of the resistance during the moving operation of the column bracket. As a basic structure of this mechanism, while fixing members for connecting and fixing the column bracket in a predetermined position and mounted portions of the column bracket mounted in a predetermined position cause each other to undergo plastic deformation, and the impact energy is absorbed in their deformation process.
Accordingly, if the mounted portions of the column bracket are provided with shapes that allow deformation to take place easily, the response to the impact can be made sensitive. On the other hand, however, the amount of absorption of the impact energy becomes small, so that such a structure is unsuitable for a large impact. In contrast, if the mounted portions of the column bracket are provided with shapes that make it difficult for deformation to take place easily, the response to the impact becomes less sensitive, and it is difficult to respond to a small impact. On the other hand, however, the amount of absorption of the impact energy becomes large, so that such a structure is suitable for a large impact.
The impact which occurs in a collision of a vehicle changes in correspondence with the relative magnitude of the impact, but the shock absorbing mechanism must be able to exhibit satisfactory response to the impact whether it is large or small. In addition, the initial impact during the occurrence of a collision is very large, and the shock absorbing performance depends largely on whether or not the energy of the initial impact can be absorbed satisfactorily.
Accordingly, an object of the present invention is to provide a shock absorbing apparatus for a steering column which improves the capability of absorbing an initial shock in the shock absorbing structure which, during the occurrence of a colliding accident of a vehicle, damps a shock, protects the driver, and ensures safety when the driver hits against the steering wheel as a reaction of the collision.
To this end, in accordance with a first aspect of the invention, there is provided a shock absorbing apparatus for a steering column, comprising: a sliding capsule having a collar portion fixed immovably to a vehicle body; and a column bracket having a shock absorbing hole which is elongated in a longitudinal direction of a steering column and in which a fixing through-hole portion on one end side of the elongated hole, a first shock absorbing portion having a shaft-like member in a vicinity of the fixing through-hole portion, and a second shock absorbing portion having a crushable inner peripheral edge at a side edge of the elongated hole are substantially continuously formed in the longitudinal direction, wherein, during a collision, the collar portion bends the shaft-like member and crushes the second shock absorbing portion to thereby absorb colliding energy.
In the above-described first aspect of the invention, the shock occurring during the collision can be absorbed in two stages. Particularly with respect to the impact of the initial collision in the first stage, it is possible to absorb the impact as the collar portion of the sliding capsule bends the shaft-like member by means of bending moment, with the result that the initial impact which is most intense can be satisfactorily alleviated. Subsequently, the impact energy can be gradually absorbed by the second shock absorbing portion.
In accordance with the above-described first aspect of the invention, the shock absorbing characteristic is improved at the time when the driver hits against the steering wheel during such as a collision of the vehicle, and the installation and adjustment of the shock absorbing apparatus for a steering column can be made simple, thereby overcoming the above-described problems of the conventional art.
In accordance with a second aspect of the invention, there is provided a shock absorbing apparatus for a steering column, comprising: a column bracket having a shock absorbing hole which is elongated in a longitudinal direction of a steering column and in which a fixing through-hole portion, a first shock absorbing portion, and a second shock absorbing portion are formed in that order from a forward side of a vehicle body, the first shock absorbing portion having a shaft-like member which can be bent by the collar portion, the second shock absorbing portion being formed in a shape of an elongated hole and having at least one of widthwise inner peripheral edges formed as a crushable inner peripheral edge; a sliding capsule having a collar portion insertable in the fixing through-hole portion of the column bracket and a resiliently supporting portion for resiliently pressing and supporting the column bracket; and a third shock absorbing portion formed as a resilient sliding friction mechanism in which the sliding capsule resiliently supports a laterally proximate portion of the shock absorbing hole by means of the resiliently supporting portion along the elongated shape formed by the first shock absorbing portion and the second shock absorbing portion, wherein the sliding capsule is immovable with respect to the vehicle body and resiliently supports the column bracket.
In the above-described second aspect of the invention, advantages are offered in that, firstly, it is possible to improve the shock alleviating capability during the collision, and that, secondly, it is possible to simplify the structure.
To give a more detailed description of the above-described advantages, the fixing through-hole portion, the first shock absorbing portion, and the second shock absorbing portion are formed in the shock absorbing hole. The first shock absorbing portion is made bendable by relative collision with the collar portion. Namely, as the collar portion collides against the shaft-like member due to the impact of the collision, the collar portion bends the shaft-like member 4a by means of bending moment, and the initial intense shock is absorbed in that bending process.
Further, after the shaft-like member is bent by the collar portion, the collar portion moves to the second shock absorbing portion, and the impact energy is absorbed by the second shock absorbing portion. Further, in addition to the absorption of impact energy by the first shock absorbing portion and the second shock absorbing portion, the impact energy absorption can be concurrently effected by the third shock absorbing portion formed as the resilient sliding friction mechanism by the resiliently supporting portion of the sliding capsule and a laterally proximate portion of the shock absorbing hole. By virtue of the resilient sliding of the resilient sliding friction mechanism, the relative movement of the collar portion and the column bracket can be effected stably and smoothly, thereby making it possible to improve the stability of the shock absorbing operation.
Thus, as the absorption of impact energy due to the collision is effected in two stages by the collar portion and by the first and second shock absorbing portions, and the third shock absorbing portion synergistically effects energy absorption as the resilient sliding friction mechanism along the longitudinal direction of the shock absorbing hole, whereby the shock can be received starting with the initial stage of shock absorption, and the shock is damped substantially. As a result, even if the driver hits against the steering wheel during a collision, the shock can be diminished remarkably.
In accordance with a third aspect of the invention, in the invention according to the first or second aspect of the invention, the shaft-like member of the first shock absorbing portion is formed in such a manner as to project from one inner peripheral edge of the first shock absorbing portion toward another inner peripheral edge thereof in a widthwise direction of the first shock absorbing portion and to be inclined toward the fixing through-hole portion.
In the above-described third aspect of the invention, since the shaft-like member of the first shock absorbing portion is formed such that only one longitudinal end thereof is formed continuously at the fixing through-hole portion of the shock absorbing hole, the shaft-like member of the first shock absorbing portion is of a cantilevered type. For this reason, when the collar portion has undergone relative collision with the shaft-like member, bending moment is applied to the shaft-like member, so that the shaft-like member is easily bent at its joint portion, thereby making it possible to further improve the shock absorbing characteristic.
Next, in accordance with a fourth aspect of the invention, in the invention according to the first or second aspect of the invention, the shaft-like member of the first shock absorbing portion is formed continuously from one inner peripheral edge of the first shock absorbing portion to another inner peripheral edge thereof in a widthwise direction of the first shock absorbing portion. As a result, the absorbing resistance during the initial impact can be made strong, and the shock absorbing characteristic depending on the type of vehicle can be adjusted appropriately.
In accordance with a fifth aspect of the invention, in the invention according to any one of the first to fourth aspects of the invention, a bending assisting portion is formed in a vicinity of a joint portion of the shaft-like member contiguous to an inner peripheral edge of the shock absorbing hole. As a result, when the collar portion has undergone relative collision with the shaft-like member during the occurrence of a collision, bending moment is applied to the shaft-like member and bending stress is applied to its joint portion, so that the shaft-like member is easily bent at the joint portion, thereby making it possible to further improve the shock absorbing characteristic.
In accordance with a sixth aspect of the invention, in the invention according to any one of the first to fifth aspects of the invention, the shock absorbing apparatus for a steering column further comprises: a cutaway slot portion which is formed in a vehicle body rear-end portion of the column bracket in such a manner as to be open at a rear end of the column bracket; a sliding capsule having a collar portion and a resiliently supporting portion for resiliently pressing and supporting the column bracket, the sliding capsule being fitted to the cutaway slot portion and adapted to resiliently support the column bracket and to be disengaged from the cutaway slot portion of the column bracket during the collision; and a third shock absorbing portion disposed in a laterally proximate portion of the first shock absorbing portion and the second shock absorbing portion, the third shock absorbing portion being formed as a resilient sliding friction mechanism using the sliding capsule for resiliently supporting the laterally proximate portion of the shock absorbing hole in its longitudinal direction by means of the resiliently supporting portion.
In accordance with the above-described sixth aspect of the invention, the column bracket can be mounted stably and securely at normal times. Meanwhile, during a collision, as the sliding capsule is disengaged from its support in the cutaway slot portion in the column bracket, which stabilizes the initial relative movement of the collar portion of the sliding capsule and the first shock absorbing portion in the shock absorbing hole, thereby satisfactorily alleviating the initial shock. Subsequently, the impact energy is gradually absorbed by the second shock absorbing portion. Thus these shock absorbing structures act synergistically, thereby making it possible to effect very satisfactory shock absorption.
In addition, since the third shock absorbing portion is formed as the resilient sliding friction mechanism in conjunction with the first and second shock absorbing portions, the third shock absorbing portion effects the shock absorbing operation starting from the initial stage of the shock together with the first shock absorbing portion. Thus even when the shock absorbing operation moves from the first shock absorbing portion to the second shock absorbing portion, the third shock absorbing portion participates in the shock absorbing operation. Hence, the impact energy during the collision can be alleviated satisfactorily, and the movement to the second shock absorbing portion is allowed to take place.
Next, in accordance with a seventh aspect of the invention, there is provided a shock absorbing apparatus for a steering column, comprising: a pair of cutaway slot portions which are formed in a vehicle body rear-end portion of a column bracket in such a manner as to be open at a rear end of the column bracket; a pair of rear shock absorbing portions each located on an open side of the cutaway slot portion and each having a shaft-like member bendable by a predetermined load; and sliding capsules each having a collar portion and a resiliently supporting portion for resiliently supporting the column bracket, the collar portion being insertable between a front-side inner peripheral edge of the cutaway slot portion and the shaft-like member, wherein the sliding capsules are respectively fitted to the pair of cutaway slot portions and a pair of shock absorbing holes formed in a vehicle forward-side portion of the column bracket along a longitudinal direction of the steering column, and wherein the sliding capsules are immovable with respect to the vehicle body and resiliently support the column bracket.
In the above-described seventh aspect of the invention, the column bracket is structured such that the column bracket at the two shock absorbing holes and the two cutaway slot portions is fixed by means of the sliding capsules. Accordingly, the column bracket can be mounted stably and securely at normal times. Meanwhile, during a collision, each collar portion relatively collides against the rear shock absorbing portion formed in each cutaway slot portion and serves to softly absorb the initial impact. The subsequent absorption of the impact is effected by the two impact absorbing holes, thereby making it possible to obtain a balanced shock absorbing capability.